RFR: JDK-8174994: SA: clhsdb printmdo throws WrongTypeException when attached to a process with CDS

[Jini George]

I agree with the need of testing as much as we can. I could do something 
on the lines of how other debuggers like LLDB test: if we can't find the 
core file location, check for "|" at the beginning of a line in the 
/proc/sys/kernel/core_pattern file -- and fail with a message stating 
that the system is using a crash reporting tool.

Thank you,
Jini.

On 4/18/2018 12:40 PM, David Holmes wrote:
> My 2c ...
> 
> We have to have tests that can test core file attaching capability - 
> else we don't know it works. So we have to try and generate a core file.
> 
> But, we have to expect that in many cases no core file will be generated 
> even if the hs-err file claims it was. For example my primary local 
> testing system never generates core files even though it claims to:
> 
> # Core dump will be written. Default location: Core dumps may be 
> processed with "/usr/share/apport/apport %p %s %c" (or dumping to /
> export/users/dh198349/valhalla/repos/valhalla-dev/open/test/jdk/core.29848)
> 
> apport isn't even installed, even though core_pattern lists it.
> 
> Cheers,
> David
> 
> On 18/04/2018 4:36 PM, Yasumasa Suenaga wrote:
>> 2018-04-18 15:05 GMT+09:00 Jini George <jini.george at oracle.com>:
>>> Thank you very much, Yasumasa, for pointing this out. You are right 
>>> -- this
>>> would fail in the Linux systems if systemd-coredump is enabled.
>>>
>>> I plan to file an enhancement request to address this issue (wrt
>>> systemd-coredump) separately since this would apply to other coredump
>>> generating test cases also like:
>>> test/hotspot/jtreg/compiler/ciReplay/TestSAServer.java.
>>
>> I agree with you, but...
>>
>>>  From what i can gather, i think we might be able to at least partially
>>> address this by using
>>>
>>> coredumptl -o <desired_core_path> dump <pid of the crashed process>
>>>
>>> in the test cases, provided the kernel.core_pattern variable is not 
>>> set to
>>> "|/bin/false".
>>>
>>> Let me know if you are not OK with this.
>>
>> IMHO it is not good.
>> Some Linux distros use other coredump collector. For example, RHEL 6
>> uses ABRT, Ubuntu uses Apport, Fedora uses systemd-coredump.
>> Hence I think we should disable all tests which requires core images
>> for Linux like a Windows platform.
>>
>>
>> Thanks,
>>
>> Yasumasa
>>
>>
>>> Thank you,
>>> Jini.
>>>
>>>
>>>
>>>
>>> On 4/14/2018 7:39 PM, Yasumasa Suenaga wrote:
>>>>
>>>> Hi Jini,
>>>>
>>>> ClhsdbCDSCore.java:
>>>>     Can this test work on modern Linux?
>>>>     AFAIK modern Linux contains systemd-coredump to gather core 
>>>> images. So
>>>> I concern ClhsdbCDSCore.java fails in the future.
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> On 2018/04/12 13:21, Jini George wrote:
>>>>>
>>>>> Ping: Gentle reminder !
>>>>>
>>>>> Thanks,
>>>>> Jini.
>>>>>
>>>>> On 4/6/2018 9:51 PM, Jini George wrote:
>>>>>>
>>>>>> Hello!
>>>>>>
>>>>>> Requesting reviews for: 
>>>>>> https://bugs.openjdk.java.net/browse/JDK-8174994
>>>>>> Webrev: http://cr.openjdk.java.net/~jgeorge/8174994/webrev.00/
>>>>>>
>>>>>> While trying to identify the type given an address, a 
>>>>>> WrongTypeException
>>>>>> was getting thrown with various clhsdb commands (like printmdo, 
>>>>>> jstack,
>>>>>> etc). This was since SA tries to map an address to a hotspot C++ 
>>>>>> type by
>>>>>> comparing the vtable address to the vtable address values of known
>>>>>> types. With CDS, since the vtables are copied over for the Metadata
>>>>>> classes, the vtable addresses themselves don't match (though, of 
>>>>>> course,
>>>>>> the contents will), and SA errors out.
>>>>>>
>>>>>> The fix has been implemented by making changes to read in the md 
>>>>>> region
>>>>>> (consisting of the c++ vtables) of the CDS archive in SA, and mapping
>>>>>> the vtable addresses to the corresponding metadata type 
>>>>>> (ConstantPool,
>>>>>> InstanceKlass, InstanceClassLoaderKlass, InstanceMirrorKlass,
>>>>>> InstanceRefKlass, Method, ObjArrayKlass, TypeArrayKlass).
>>>>>>
>>>>>> For corefiles, an additional modification has been done to have the
>>>>>> replicated FileMapHeader structure (from
>>>>>> src/hotspot/share/memory/filemap.hpp, which is replicated in SA in
>>>>>> ps_core.c), to be in sync with the corresponding definition in
>>>>>> src/hotspot/share/memory/filemap.hpp.
>>>>>>
>>>>>> Test cases to test both live and corefile debugging are being 
>>>>>> added with
>>>>>> this. These and other SA tests pass on Mach5.
>>>>>>
>>>>>> Thanks,
>>>>>> Jini.
>>>>>
>>>>>
>>>